Polymeric composition and method

ABSTRACT

A molding composition which is water cured to a polyurea bound material prepared by mixing between about 90 and 99 wt. percent sand and between about 1 and 10 wt. percent of a multifunctional isocyanate bonding agent which is the product of the phosgenation of the condensation product of an aldehyde and aromatic amine or an aldehyde, aromatic amine and a phenol.

United States Patent 119 Inventors: Hans Albrecht Meyer-Stoll,

Rheinkamp; Manfred Lottermoser, Barienrode, both of Germany Deutsche Texaco Aktiengesellschaft, Hamburg, Germany Filed: Feb. 9, 1972 Appl. No.: 224,927

Assignee:

References Cited UNITED STATES PATENTS 5/1944 Pratt 260/725 X 2/1951 Gleim .Q. 260/725 X /1968 Robins et al 260/DIG. 2/1969 Walker et al. 260/DIG. 40

Meyer-Stoll et al. Oct. 1, 1974 POLYMERIC COMPOSITION AND 3,616,046 10/1971 Benzinger et al. 260/515 x METHOD OTHER PUBLICATIONS Chemical Abstracts, 62: 463e & 65: 7393f. (published 1963 and 1966 resp.)

J. H. Saunders and K C. Frisch, Polyurethanes, Chemistry and Technology, (1964) p. 301. v

Primary Examiner-Allan Lieberman Assistant ExaminerS. M. Person Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries [57] ABSTRACT A molding composition which is water cured to a polyurea bound material prepared by mixing between about and 99 wt. percent sand and between about 1 and 10 wt. percent of a multifunctional isocyanate bonding agent which is the product of the phosgenation of the condensation product of an aldehyde and aromatic amine or an aldehyde, aromatic amine and a phenol.

V 9 Claims, N0 Drawings BACKGROUND OF INVENTION It is known to mix quartz sand with aromatic diisocyf anates and triisocyanates and solutions of phenolformaldehyde resin in which the phenol nuclei contain methylol groups and to transfer these mixtures into core boxes in which they are treated with triethylamine-containing inert gas, for example, with nitrogen containing triethylamine. The triethylamine acts as a catalyst in the reaction between the isocyanate groups and the methylol groups to form urethane groups. The polyurethane so formed binds the quartz sand together to produce solid mold from the core boxes.

These polyurethane bonding agents formed by the foregoing method have the disadvantage in that the period of time in which sand mixtures thereof are workable is limited. The reaction resulting in the formation 20 of the polyurethane starts during the mixing operation and before the triethylamine takes effect so that portions of the mixed molding batches have to be frequently discarded for reasons that they cannot be completely worked before the tion has progressed too far. An additional disadvantage of the aforementioned method of forming cores is the danger of exposure, poisoning and injury by' cauterization in the handling of triethylamine and a triethylamine-inert gas mixture.

In order to reduce, though not completely to avoid these dangers, it has been proposed to. use steam or water vapor or an aqueous aerosol instead of a triethylamine containing inert gas mixture to incorporate triethylamine or other tertiary amine in the sand mixture which contains the isocyanate and to employ polyesters instead of phenolformaldehyde resins. Water is supplied to assist the formation of the polyurea by the catalytic action of the tertiary amine present in the sand mixture and to assist the solidification of the foundry molded parts formed from the sand mixture. When this proposal was tested, it was found, however, that the properties of the sand mixtures of this kind undesirably changed very quickly immediately upon completion of the mixing operation and the desired solidifying effect was inadequate to enable moldable or even castable moldable parts to be produced.

THE INVENTION parts which may be removed polyurethane forming reacat a temperature between about 30 diamine, m-phenylenediamine, ,Aniline is the preferred aromatic in a mole ratio ofsaid amine to said phenol in said (2) a condensation temperature of between about 70 and 7 105C. and a condensation period of between about 1 and 5 hours to form an aldehyde-member condensation product. The condensation product is contacted with phosgene utilizing a mole 'ratio of initial amine to phosgene of between about 1 0.1 and 1 l, advantageously and 130C. normally for a period of between about 0.5 and 2.5 hours to form said multi-functional isocyanate binding agent.

Examples ofthe aldehydes contemplated hEein' areformaldehyde, acetaldehyde, glyoxal. Formaldehyde is the preferred aldehyde.

Examples of suitable aromatic amines contemplated herein are aniline, p-toluidine, m-toluidine, o-toluidine, o-nitraniline, m-nitraniline, p-mtraniline, o-phenylenep-phenylenediamine. amine.

Examples of the phenols contemplated herein are monohydroxybenzene, o-, m-, p-methylphenol (cresols). Monohydroxybenzene is the preferred phenol.

ln curing the sand condensation product compositions contemplated herein, the bonding agent-sand mixture is contacted with water vapor or steam wherein each mole of the water supplied reacts with two moles of the isocyanate groups formed in the phosgenation with the elimination of one mole of carbon dioxide and referred to are entirely avoided. Another object of the;

invention is to provide a molding mix in which the lirni-f tation of a short period of time in which the mix isus-g able is also avoided.

Specifically, the invention is directed to a molding: composition which is cured by contact with water to a; polyurea bound material, said molding composition comprising between about 90 and 99 wt. sand and between about 1 and 10 wt. of a multifunctional isocyanate bindingagent formed by condensing an aldehyde of the formula RCl-IO with a member selected from the group consisting of (1) aromatic amine of the formula:

a simultaneous formation of (l-IN-CONl-I) groups. This curing is normally conducted at a temperature between about 10 and 65C. utilizing a mole ratio of water to initial aromatic amine of between about 0.5 l and 5 1. Owing to the multiple functionality of the isocyanates, polyureas and polyurea derivatives are thus formed which impart the necessary solidity to the moldings with the resultant conversion of the moldings into solidfoundry mold parts. Surprisingly, the structure of the moldings are not loosened by the evolving carbon dioxide. Further, the reaction between the water and the isocyanate groups proceeds relatively quickly and the use of tertiary amine catalyst is thus dispensed with. If required, the reaction may be accelerated by the application of heat, it being particularly advantageous for moldings to be treated with steam.

The multifunctional isocyanate bonding agents are,

when too viscous, preferably used in the form of solu-.

' tions, e.g., between about 10 and wt. solution in the mixing or preparation of the molding batches. Sol- 3 vents used should be inert and have at least limited dis solving power for water, 'e.g., at least about 0.01 and 0.1 grams dissolved water per gram solvent. Suitable solvents are aromatic hydrocarbons, ketones, ethers, esters or mixtures which contain one or more of these classes of substances. Thus, for example, benzene, toluene, cyclohexanone and polyglycol ethers with esterified terminal hydroxide groups are representative of these classes oftsubstances. I

The invention is illustrated in the following examples but which are not to be construed as limitations thereof. I l I I EXAMPLE I a. The bonding agent Two hundred grams of phenol, 180 grams of a 38 wt. aqueous formaldehyde solution and 100 grams of a 5 wt. aqueous sodium hydroxide-solution were boiled under reflux forl hour. The solution was then neutralized to a p of about 7 with oxalic acid and 65 grams of aniline were added dropwise to the solution within a period of 30 minutes at reflux temperature (100C). The mixture was maintained at a reflux temperature for a further 3 hours. The aqueous'phase was separated and the removal of the water was made complete by increasing'thetemperature to l35Cl.' Any unconverted aniline was simultaneously expelled. The brown resin obtained was dissolved as a 20. wt. solution in a mixture of cyclohexanone, benzene, chlorobenzene and ortho-dichlorobenzene, .and phosgene was bubbled therethrough. Ninety-seven grams of phosgene were introduced into the solution. Upon completion of phosgenation, a portion of the solution was removed and the solvent evaporated and the resultant multifunctional isocyanato bonding agent product was analyzed and found to have a chlorine content of about 2.5 wt. Solvent from the remainder of the phosgenated solution was evaporated until a 70 wt. solution was formed'which solution was then diluted with cyclohexanone to produce a 50 wt. solution.

b. The molding composition and core composition A molding batch was produced bymixing 4 kg. of dry quartz sand, 4 grams of calcium stearate and 160 'grams of bonding agent described under (a). One portion of the molding batch was molded immediately aftertermination of the mixing operation, another portion being stored for 3 hours before it was molded. Six bending rods were molded from each batch as follows:

According to DIN 52404, a mold measuring (inside) 172.5 X 22.4 X 22.4 mm was filled with the resin-sand mixture, which was compressed by three blows with a ram exactly matching the mold and having a standard weight (6666 grams; DIN 5240l After termination of the ramming operation the molded part must have a height of 23.4 $0.3 mm. As distinct from DIN 52404 the rods were then left in the mold in order to be treated with steam or water vapor. The mold was also distinct from that used according to DIN 52404 in that it was provided with a funnel-shaped gas intake at the top and with slit nozzles or outlets on its underside. Steam admitted through the funnel-shaped gas intake was passed through the mix in the mold'for a period of 2 minutes. The mold of the bending rods formed from each batch was completed immediately after the water vapor or steam had passed through and the rods were then stored for 1 hour before their bending strength was tested as follows:

.4 I The bending-test specimen was so disposed that both its ends rested on horizontal bending-test supports, with a width L 150 mm between said supports, the axes of said supports being in a direction normalto the longitudinal axis of the bending-testspecimen. A concentrated, vertical load was applied centrally to the specimen. The load was constantly and smoothly increased until the specimen broke. The indicated mean value is derived from three specimens; test values deviating by more than 10 percent from the mean value are discarded.

c. The results The six rods tested in accordance with the above method and formed immediately upon termination of the mixing operation had an average bending strength of 19.5 kp/sq. cm. whereas the six rods formed from the molding batch that had been stored for 3 hours before 23.8 kp/sq. cm.

7 EXAMPLE II v (not in accordance with the invention) As the known commercial mixtures consist of two components only, 100 grams of a 40 wt. phenolnovolak solution in cyclohexanone were mixed with 4 kg. of quartz sand, to which 40 grams of diisocyanatodiphenylmethane were added, and the whole was then intimately mixed. As described in Example I, six bending rods were molded immediately from the mixture in accordance with DIN 52404. As these mixtures cannot be cured with water vapor, an air stream loaded with triethylamine was passed, an usual, over the filled molds.

Results v The bending rods formed immediately after termination of the mixing operation showed an average bending strength of 28.3 kp/sq. cm. in accordance with DIN 52404, whereas the resin-sand mixture that had been stored for 3 hours had solidified and could no longer be utilized to form standard rods.

We claim:

l. A molding composition curable by treating with water consisting essentially of betweenabout and99 wt..% sandan'd between 1 and.".l0 wt. multifunctional isocyanate bonding agent prepared by condensing an aldehyde of the formula RCHO'with'a member selected from the group consisting of (a) an aromatic amine of and (b) said aromatic amine and a phenol of the formula: v I

in a mole ratio of said aromatic amine to said phenol in (b) of between about 0.08 l and 0.8 l, where R, R and R are hydrogen oralkyl of from 1 to 6 carbons to form an aldehyde-member condensation product and contacting said aldehyde-member product with phosgene utilizing a mole ratio of phosgene to said aromatic amine of between about 0.1 1 l and l l to form said multifunctional isocyanate bonding agent.

2. A composition in accordance with claim 1 wherein said member is (b), said aldehyde is formaldehyde, said aromatic amine is aniline, and said phenol is monohydroxybenzene.

3. A composition in accordance with claim 1 wherein said member is (a), said aromatic amine is aniline and said aldehyde is formaldehyde.

4. A method for producing a solid sand mold consisting essentially of contacting with water a composition comprising between about 90 and 99 wt. sand and between about 1 and wt. multifunctional isocyanate bonding agent prepared by condensing an aldehyde of the formula RCHO with a member selected from the group consisting of (a) aromatic amine of the formula:

I NH;

and (b) said aromatic amine and a phenol of the formula:

where R, R and R are hydrogen or alkyl of from 1 to 6 carbons to form an aldehyde-member condensation product and contacting said aldehyde-member condensation product with phosgene utilizing a mole ratio of phosgene to said aromatic amine of between about 0.08 l and 0.8 l to form said multifunctional isocyanate bonding agent.

5. A method for producing a solid sand mold in accordance with claim 4 wherein said member is (b), said aldehyde is formaldehyde, said aromatic amine is aniline, and said phenol is monohydroxybenzene.

6. A method in accordance with claim 4 wherein said member is (a), said aromatic amine is aniline and said aldehyde is formaldehyde.

7.- A solid sand mold produced by the method of claim 4.

8. A solid sand mold produced by the method of claim 5.

9. A solid sand mold produced by the method of claim 6. 

1. A MOLDING COMPOSITION CURABLE BY TREATING WITH WATER CONSISTING ESSENTIALLY OF BETWEEN ABOUT 90 AND 99 WT. % SAND AND BETWEEN 1 AND 10WT. % MULTIFUNCTIONAL ISOCYANATE BONDING AGENT PREPARED BY CONDENSING AN ALDEHYDE OF THE FORMULA RCHO WITH A MEMBER SELECTED FROM THE GROUP CONSISTING OF (A) AN AROMATIC AMINE OF THE FORMULA:
 2. A composition in accordance with claim 1 wherein said member is (b), said aldehyde is formaldehyde, said aromatic amine is aniline, and said phenol is monohydroxybenzene.
 3. A composition in accordance with claim 1 wherein said member is (a), said aromatic amine is aniline and said aldehyde is formaldehyde.
 4. A method for producing a solid sand mold consisting essentially of contacting with water a composition comprising between about 90 and 99 wt. % sand and between about 1 and 10 wt. % multifunctional isocyanate bonding agent prepared by condensing an aldehyde of the formula RCHO with a member selected from the group consisting of (a) aromatic amine of the formula:
 5. A method for producing a solid sand mold in accordance with claim 4 wherein said member is (b), said aldehyde is formaldehyde, said aromatic amine is aniline, and said phenol is monohydroxybenzene.
 6. A method in accordance with claim 4 wherein said member is (a), said aromatic amine is aniline and said aldehyde is formaldehyde.
 7. A solid sand mold produced by the method of claim
 4. 8. A solid sand mold produced by the method of claim
 5. 9. A solid sand mold produced by the method of claim
 6. 